Objective: To study the effects and safety of Spongilla lacustris (SL) in 3% hydrogen peroxide (H2O2) on rat skin.
Material and Method: An experimental study was conducted on 3 groups of Wistar-Furth adult rats. The first group was applied with SL in H2O2; the second group with SL in 0.9% normal saline (NSS) and the control group with NSS. These agents were applied on and wiped off the rat skin weekly for four weeks, then the skin biopsies were done. The number of SL spicule and the depth of spicule penetration were examined by scanning electron microscope and by polarized light microscope respectively. Skin histopathology was determined by hematoxylin-eosin staining. The gross skin changes were observed.
Results: Under electron microscopic examination, SL was demonstrated as spicule which was sharp edged, rod-shaped and smooth surface with approximate 150-300 microns in length and 10-20 microns in diameter. Spicule retention was found in the rat skin lasted until day 3 but was undetectable on day 7. The spicules could be detected deep into stratum basalis. Comparing among three groups, the thickness of epidermis in the second group was decreased with statistically significant difference (p = 0.044) by the end of week 7. The dermal thickness of all groups was increased by age. No any gross skin alteration of all groups was observed.
Conclusion: The authors hypothesized that the spicule causes puncture that enhances H2O2 penetration into the skin. This solution was safe in the short term usage. However, the long term safety regarding granulomatous formation is still questionable.

Keywords: Spongilla lacustris, Hydrogen peroxide, Acne vulgaris, Rat skin